Generally, mobile communications systems are made up of a plurality of cells. Each cell provides a radio communications center through which a mobile station establishes a call or other communications session with another mobile station or a terminal connected to either a circuit-switched network (e.g., public-switched telephone network or PSTN) or a packet-switched data network. Typically, each cell includes a radio base station, with each base station coupled to a switching center that controls processing of calls or other communications sessions between or among mobile stations or between mobile stations and terminals connected to a circuit-switched or a packet-switched network.
Various wireless protocols exist for defining communications in a wireless network. One type of protocol is based on the time-division multiple access (TDMA) technology, such as the TIA/EIA-136 standard or the Global System for Mobile (GSM) standard. Another type of protocol for wireless communications is based on the code-division multiple access (CDMA) technology. CDMA is a spread spectrum wireless communications protocol in which transmission is based on the spread spectrum modulation technique to allow many users to have access to the same band of carriers.
Traditionally, wireless networks were designed for carrying circuit-switched voice traffic. However, with the wide availability of the Internet and intranets, packet-switched communications (e.g., web browsing, electronic mail, instant messaging, electronic gaming, and so forth) have become common. As a result, third generation (3G) and beyond wireless technologies are being developed to provide higher bandwidth and more efficient packet-switched communications (of data as well as voice and other forms of real-time data) over wireless networks.
Packet-switched wireless communications protocols have been developed for both TDMA and CDMA. For example, in the CDMA context, a CDMA 2000 family of standards has been developed that is capable of supporting both traditional circuit-switched traffic as well as packet-switched traffic.
The first phase of CDMA 2000 is referred to as 1xRTT (also referred to as 3G1X or 1X), which is designed to increase voice capacity as well as to support data transmission speeds that are faster than typically available. In addition, for even higher data rates in packet-switched communications, a High Rate Packet Data (HRPD) wireless technology has been developed. HRPD is defined as TIA/EIA/IS-856, “CDMA 2000, High Rate Packet Data Air Interface Specification,” which is adopted by the TIA. The HRPD technology is also referred to as the 1×EV-DO or 1×EV technology. 1×EV-DO provides relatively high data transfer rates over the air interface between mobile stations and base stations (usually faster than 1xRTT rates).
In a 1×EV-DO system, a mobile station can specify the rate of data to be communicated in the forward wireless link (which is the wireless link from the base station to the mobile station). This is specified by the mobile station in a defined indication, referred to as the data rate control (DRC) channel, and can be a function of a specific quality of service to which the mobile station user has subscribed. Given the data rate specified by the mobile station, the 1×EV-DO wireless access equipment (sometimes referred to as an access network) specifies a size of a physical layer packet to be communicated between the wireless access equipment and the mobile station. A physical layer packet is a packet defined by the physical layer of the air interface for carrying certain control information and traffic data over the air interface. Depending upon the size of the physical layer packet, the IS-856 standard specifies that one to four higher level packets, such as medium access control (MAC) packets, can be carried in the physical layer packet. Thus, if a low data rate is specified, then the physical layer packet has a smaller size and can carry fewer packets. On the other hand, if a high data rate is specified, then the physical layer packet has a larger size and can carry a larger number of packets.
However, the data rate that is specified by the mobile station may not be the data rate that is actually needed by, or supplied to, application software in the wireless access equipment. If the mobile station specifies a high data rate, which means that the physical layer packet is larger, then any unused space in the physical layer packet is filled with filler information. The physical layer packet containing useful information and the filler information is then sent to the mobile station over the forward wireless link. Filling the physical layer packet with filler information wastes resources of the forward wireless link.